The invention relates generally to semiconductor integrated circuit (IC) packages and more particularly, it relates to an improved ball grid array (BGA) package which contains multiple IC devices electrically isolated from each other.
Conventionally, IC devices are mounted on a PC board and electrical isolation of the IC devices is maintained on the board. In order to efficiently use spaces on the PC board, there are packages which contain multiple IC devices, commonly referred to as multi-chip modules (MCM's). These devices are connected to each other inside the package and share both the power and ground levels. Simple packages, which contain two IC devices and maintain them electrically isolated within a single package, are also used. The IC devices within such simple packages are limited to simple transceivers and DC to DC converters, and such packages are limited to DIP (dual in package), SOJ (small outline J lead), QFP (quad flat package) and high QFP. These simple packages are typically small in size and the number of pins for these packages varies from less than 48 (for DIP and SOJ) to 144 (for high QFP) pins. They are ideal for simple IC devices.
Attempts have been made to maintain electrical isolation of IC devices of complex designs within a single package. Such efforts, however, have not proved to be successful due to a number of factors including the difficulties associated with high pin density of complex IC devices. For example, a multi-layered BGA package typically includes 64 to 1000 pins on a 2 inch by 2 inch area. Also, there are obstacles associated with the spacing requirements between the internal IC devices to maintain a small package footprint.
Therefore, there is a need for implementing electrical isolation of large scale IC devices of complex designs within a single package.